MariaDB 10.0 had a stable release last month. It is a good time to take a look and see how it compares to the stable version of MySQL, MySQL 5.6 (as for Percona Server, it doesn’t have its own optimizer features).
Changelogs and release notes have all the details, but it’s difficult to see the big picture. So I went for diagrams, and the result is a short article titled What is the difference between MySQL and MariaDB query optimizers. It should give one a clue about what are the recent developments in query optimizers in MySQL world.

In case you’re interested in details about optimizer features in MariaDB 10.0, I’ve shared slides from a talk about MariaDB 10.0 query optimizer.